Across insect genomes, the size of the cytochrome P450 monooxygenase (
Major habitat transitions, such as those from marine to freshwater habitats or from aquatic to terrestrial habitats, have occurred infrequently in animal evolution and may represent a barrier to diversification. Identifying genomic events associated with these transitions can help us better understand mechanisms that allow animals to cross these barriers and diversify in new habitats. Study of the
- NSF-PAR ID:
- 10461665
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Evolutionary Biology
- Volume:
- 32
- Issue:
- 6
- ISSN:
- 1010-061X
- Format(s):
- Medium: X Size: p. 580-591
- Size(s):
- p. 580-591
- Sponsoring Org:
- National Science Foundation
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Abstract CYP ) gene superfamily varies widely.CYP ome size variation has been attributed to reciprocal adaptive radiations in insect detoxification genes in response to plant biosynthetic gene radiations driven by co‐evolution between herbivores and their chemically defended hostplants. Alternatively, variation inCYP ome size may be due to random “birth‐and‐death” processes, whereby exponential increase via gene duplications is limited by random decay via gene death or transition via divergence. We examinedCYP ome diversification in the genomes of seven Lepidoptera species varying in host breadth from monophagous (Bombyx mori ) to highly polyphagous (Amyelois transitella ).CYP ome size largely reflects the size of Clan 3, the clan associated with xenobiotic detoxification, and to some extent phylogenetic age. Consistently across genomes, familiesCYP 6,CYP 9 andCYP 321 are most diverse andCYP 6AB ,CYP 6AE ,CYP 6B,CYP 9A andCYP 9G are most diverse among subfamilies. Higher gene number in subfamilies is due to duplications occurring primarily after speciation and specialization (“P450 blooms”), and the genes are arranged in clusters, indicative of active duplicating loci. In the parsnip webworm,Depressaria pastinacella , gene expression levels in large subfamilies are high relative to smaller subfamilies. Functional and phylogenetic data suggest a correlation between highly dynamic loci (reflective of extensive gene duplication, functionalization and in some cases loss) and the ability of enzymes encoded by these genes to metabolize hostplant defences, consistent with an adaptive, nonrandom process driven by ecological interactions. -
Summary Plants have mechanisms to recognize and reject pollen from other species. Although widespread, these mechanisms are less well understood than the self‐incompatibility (
SI ) mechanisms plants use to reject pollen from close relatives. Previous studies have shown that some interspecific reproductive barriers (IRB s) are related toSI in the Solanaceae. For example, the pistilSI proteins S‐RN ase andHT protein function in a pistil‐sideIRB that causes rejection of pollen from self‐compatible (SC ) red/orange‐fruited species in the tomato clade. However, S‐RN ase‐independentIRB s also clearly contribute to rejecting pollen from these species. We investigated S‐RN ase‐independent rejection ofSolanum lycopersicum pollen bySC Solanum pennellii LA 0716,SC .Solanum habrochaites LA 0407, andSC Solanum arcanum LA 2157, which lack functional S‐RN ase expression. We found that all three accessions expressHT proteins, which previously had been known to function only in conjunction with S‐RN ase, and then usedRNA i to test whether they also function in S‐RN ase‐independent pollen rejection. Suppressing expression inHT SC S. pennellii LA 0716 allowsS. lycopersicum pollen tubes to penetrate farther into the pistil in suppressed plants, but not to reach the ovary. In contrast, suppressingHT expression inHT SC .Solanum habrochaites LA 0407 and inSC S. arcanum LA 2157 allowsS. lycopersicum pollen tubes to penetrate to the ovary and produce hybrids that, otherwise, would be difficult to obtain. Thus,HT proteins are implicated in both S‐RN ase‐dependent and S‐RN ase‐independent pollen rejection. The results support the view that overall compatibility results from multiple pollen–pistil interactions with additive effects. -
Proliferating cell nuclear antigen (
PCNA ) plays critical roles in eukaryoticDNA replication and replication‐associated processes. It is typically encoded by one or two gene copies (pcna ) in eukaryotic genomes. Recently reported higher copy numbers ofpcna in some dinoflagellates raised a question of how this gene has uniquely evolved in this phylum. Through real‐timePCR quantification, we found a wide range ofpcna copy number (2–287 copies) in 11 dinoflagellate species (n = 38), and a strong positive correlation betweenpcna copy number and genome size (log10–log10transformed). Intraspecificpcna diverged up to 21% and are dominated by nonsynonymous substitutions, indicating strong purifying selection pressure on and hence functional necessity of this gene. By surveyingpcna copy numbers in eukaryotes, we observed a genome size threshold at 4 pgDNA , above which more than twopcna copies are found. To examine whether retrotransposition is a mechanism ofpcna duplication, we measured the copy number of retroposedpcna , taking advantage of the 22‐nt dinoflagellate‐specific spliced leader (DinoSL ) capping the 5′ end of dinoflagellate nuclear‐encodedmRNA s, which would exist in the upstream region of a retroposed gene copy. We found that retroposedpcna copy number increased with totalpcna copy number and genome size. These results indicate co‐evolution of dinoflagellatepcna copy number with genome size, and retroposition as a major mechanism ofpcna duplication in dinoflagellates. Furthermore, we posit that the demand of faithful replication and maintenance of the large dinoflagellate genomes might have favored the preservation of the retroposedpcna as functional genes. -
Summary We investigated the molecular basis and physiological implications of anion transport during pollen tube (
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Summary The evolution of
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